The invention relates to vascular filters intended to capture embolic particles, by means of filtration, that may arise from the treatment of diseased blood vessels.
Percutaneous intravascular treatment of diseased blood vessels, such as angioplasty or stent placement procedures, may result in the dislodgment of loose plaque or thrombus which then migrate downstream. Since any such particles may become lodged in other vessels, effectively preventing blood from passing into a the organ which that vessel supplies, and potentially causing serious end-organ damage which may be difficult or impossible to reverse, effective avoidance of this complication is extremely important.
One of the early methods of removing residual matter resulting from an angioplasty procedure using a balloon catheter involved maintaining the balloon in an inflated state while performing the intended intervention on the blood vessel. In this manner, much of the material could be removed without an extraneous filtering device. However, the reliability of such a procedure, especially for blood vessels supplying oxygen to the brain, necessitated substantial improvement.
Previous attempts at vascular filters have included a vena caval filter, which is permanently deployed in the vena cava via a peripheral vein in order to prevent embolisation of blood clots from the veins of the legs to the lungs, thus avoiding potentially serious and life threatening pulmonary embolism. The filter typically included a plurality of anchoring legs bent outwardly to form hooks to penetrate the vessel wall and secure the filter permanently in position. An example of such a device is disclosed in U.S. Pat. No. 4,619,246.
While conventional vena caval filters work well for their intended purposes, they suffer from the disadvantages associated with damaging the inner vessel wall through the inherent penetrating nature of the hooks, and blockage caused over time as the filter becomes endothelialized with the blood vessel inner wall or as recurrent blood clots obstruct blood flow through the filter.
In an effort to resolve the problems with vena caval filters, those skilled in the art have developed temporary filtering mechanisms that attach to an angioplasty catheter and withdraw from the vasculature following the procedure. One proposal, disclosed in U.S. Pat. No. 4,723,549, discloses a collapsible wire mesh filter disposed around the distal portion of a wire guided balloon catheter. A filter balloon is positioned beneath the wire mesh and inflates radially outwardly to expand the wire mesh when inserted downstream of a stenosed blood vessel. As the vessel is treated, fine particles dislodged from the stenosis are trapped by the mesh and subsequently removed with the filter and catheter following the procedure.
A similar device and method, disclosed in U.S. Pat. No. 4,873,978 includes a balloon catheter directed through a vasculature by a guide wire. The catheter mounts a strainer at its distal end that responds to actuation of a separate control wire to open and close a plurality of tines capable of retaining dislodged particles from a treated stenosis.
The temporary filter devices described above require additional lumens and/or control wires beyond those associated with the catheter guide wire to control the filtering procedure. The extra lines and wires typically create added complexity for the operator. Moreover, it is often desirable to adjust the relative spacing between the deployed filter and the stenosed area due to the potential presence of additional blood vessels proximate the stenosis. Because the conventional filters are mounted to the distal ends of the respective catheters, adjustments during the procedure typically cannot be made. Furthermore, the use of balloon catheters and stent devices involving the same procedure could not be achieved with filter protection in place.
Therefore, a need exists in the art for a temporary vascular filter which does not require additional control wires and catheter lumens. Moreover, the need exists for such a filter in which adjustment of the filter with respect to a lesioned vessel area, and allows for the exchange of various types of devices (e.g., balloon catheters, stents, etc.), while maintaining protection against distal emboli. The temporary vascular filter guide wire of the present invention satisfies these needs.
The apparatus and method of the present invention minimizes the complexity associated with manipulating a vascular filter during an angioplasty or stent placement procedure by incorporating the filter on a catheter guide wire such that the guide wire performs the dual functions of guiding the catheter to a stenosed location, and filtering dislodged particles flowing downstream of the treated area. Moreover, because the guide wire operates independently of the catheter, relative spacing between the filter and the lesion location may be easily altered, and exchanges of various devices over the wire are possible.
To realize the advantages described above, the invention, in one form, comprises a vascular filter guide wire for directing precision placement of a catheter or stent proximate a lesion and selectively filtering particulate debris dislodged by treatment. The guide wire includes an actuating mechanism and an elongated flexible core wire having a proximal end mounted to the actuating mechanism and a distal end for insertion through a vasculature to a position downstream of the lesion. A tubular flexible shaft is slidably disposed telescopically along the core wire. The shaft includes a proximal portion affixed to the actuating mechanism in movable relation to the wire proximal end, and a distal portion disposed inwardly from the core wire distal end for placement downstream of the lesion. A collapsible strainer coupled to the shaft distal portion is operable, in response to relative displacement between the shaft and the core wire, to radially extend outwardly within the vasculature so that it can trap particulate matter arising from the treatment of the lesion.
In another form, the invention comprises a catheter system for treating a lesion within the vasculature. The catheter system includes a catheter having a lesion treatment device and a vascular filter guide wire for directing the catheter to the lesion. The guide wire includes a collapsible filter for deployment downstream of the catheter to trap particulate matter dislodged from the lesion during the treatment.
In yet another form, the invention comprises a method of filtering particulate debris from a vasculature caused by treatment of a lesion with a catheter having a lesion treatment portion, the catheter being guided to the location of the lesion by a vascular filter guide wire having a core wire, a slidable shaft, and a collapsible filter mounted on the shaft and deployable upon relative displacement between the core wire and the shaft. The method includes the steps of first guiding the vascular filter guide wire through the vasculature along a predetermined path to a lesion such that the filter is disposed downstream of the lesion. The next step involves deploying the filter radially outwardly by shifting the shaft relative to the core wire. Then, the catheter is run over the guide wire along the predetermined path to position the lesion treatment portion of the catheter proximate the lesion. The method continues by treating the lesion according to a predetermined procedure then maintaining the filter in a deployed position until the risk of particulate matter is substantially eliminated. The catheter is then withdrawn from the vasculature and the filter retracted radially inwardly by shifting the shaft back to the original position. The method then concludes with the step of removing the guide wire from the vasculature.
One embodiment of the invention comprises a vascular filter for controllably expanding within a blood vessel to trap particulate matter loosened from treatment of a lesion. The filter is responsive to relatively shiftable control elements to expand and retract and includes a braid comprising a composite metallic/polymeric material. The material includes a plurality of metallic filaments mounted to the respective shiftable shaft and core wire to define a support structure and a polymeric mesh interwoven with the metallic filaments to define a strainer.
Another form of the invention comprises a method of fabricating a vascular filter. The method includes the steps of first selecting a mandrel having a plurality of consecutively connected forms and weaving a continuous layer of braid over the consecutively connected forms. The method proceeds by bonding the braid filaments at spaced apart sections between respective forms and separating the respective braided forms at the bonded sections. The forms are then removed from the layer of braid.